Process for extracting tin mixture from lead and tin alloys



MayI 15, 192s. 1,669,580

' M. SPEICHERT PROCESS FOR EXTRACTING TIN MIXTURE FROM LEAD AND TINALLOYS Filed Sept. 18. 1926 2 Sheets- Sheet 1 May 'S/OL'CherZ" May 159192s. 1,669,580

M. SPEICHERT PROCESS FOR EXTRACTING TIN MIXTURE FROM LEAD AND TIN ALLOYSFiled Sept. 18. 1926 2 Sheets-$11691 2 Patented May 1928,

l UNITED psr-Atras mix srnrcnnnr, or BEBLIN-TEMPELHOF, GERMANY.

Pnocnss For. nx'rnacrINe TIN mix'runn :rnom Laan ann TIN nous.

Application filed September 18, 1926, Serial No. 136,299, and in Germany@ctober 11,`1924.

This invention relates to a process 'for extracting tin mixture fromlead and -'tin ,alloys containing antimony and copper or one of thesemetals with. or without small t3 amounts of other metals, 1 or forpreparing bearing metals or the like free trom lead or having" only asmall proportion theri.

Liuation or segregation was hitherto resorte to as a means ci extractingcompol@ nents from alloys or extracting alloys of dissimilar compositiontherefrom by melting the easily liqueed components out of the solidremaining residue of theinitial material. This method of proceedinghowever l@ has only a limited number of applications because thecomposition of the products thus obtained is not always as expected,chiey for the reason that the temperature cannot` be regulated' withsulicient accuracy, the 'consequence being that the melted-out metal isnot uniform in composition. v

Furthermore, the old liquation process must be carried through severalstages or steps inorder to secure an alloy of fairly accuratecomposition. h

The rocess of my invention overcomes these dlculties encountered in theliquation process by the substitution therefor of a single stage or stepwhich correspondsl to and yet is essentially different from the laststep of the liquation'process, and by which an alloy of accuratecomposition can be obtained. v

I have found that it is possible to extract 85 individual components oralloys of dissimilar 4but quite definite composition from metal alloysabove referred to by first melting the wholeof the;- alloy andthereafterl slowly allowing it to cool. Certain componentsof 40 thealloys crystallize individually or as .a

mixture while other components remain 'luidv and may be removed in thatAstate from the melting furnace. For allowing the fluid portion to bedrawn off the molten metal bath should have a certain depth to enablethe solid and liquid portion to separate from each other well. Thisrenders it possible to separate individual components or alloys ofdeiinite composition (more particularly eutectic mixtures having adefinite melting point) by suitably regulating the temperature andselecting the composition of .the charge. I

Taking as an example an alloy of tin, an-

timony, lead and copper, as available. inr

scrap from bearing metal, melting the said alloy as just outlined andallowin it to cool slowly, antimony and copper. reac the solid statewhile tin and lead with a practically negligible percentage oi antimonyand cope per remain duid. The li uid nflixture forms the so-called tinmixture suitableas a main component of solder.

ils another example, the initial material may be made up by mixing scrapof dissimilar composition so that tin and lead in the molten materialare in proportion of their eutectic mixture. lin this case there is apractically complete separation of the eutectic mixturefof tin and leadwith the exceedingly small percentage of antimony and copper, on the onehand, and oi copper and antimony, on the other hand. The formation andremoval of the eutectic mixture are of course not prevented byan excessof tin or lead,v but the amount oimetal in excess is lost as itsolidiies with the antimony and the copper. f

The above method 'of proceeding is likewise suitable for makingbearingmetals or the like free from lead or having only a smallproportionthereof. To this end the charge must have' an ample proportionof copper and a large excess of tin. Lead may thus be completelyextracted by removing the mixture which contains the whole (orsubstantially the whole) of the lead and which remains fluid when ,themolten material cools down, leaving behind an alloy of tin,

may of course contain the minpnquantities of other metals abovereferred' to.

charge composed of 44% tin, 32% lead, 20% antimony and 4% copper ismelted and allowed to cool to 182 C. The mixture of 55 and 3.5 partsoff4 antimony, remains Huid and is drawn olf while the remainingantimony and copper are left behind in the solid state.

parts of tin and 41.4 parts of lead, with an lallowable proportion Aof0.1 part of copper Ewample Z, for making bearing metal poor n Zeadf-Acharge composed of 70% tin, 13% lead, 12% antimony and,5% copperismelted and allowed to cool to 182 C. Out of 100 parts of the charge 30parts of tin mixture are obtained in the form of a fluid mixture (55parts ofl tin and 41.4 parts of lead, with the allowable proportion of0.1% copper and 3.5% antimony) and parts of solid bearing metal areobtained, containing 76% tin, and 16% antimony, 7% copper and 1% lead.

The process can be carried out in a similar manner, if the startingmaterial, besides lead and tin, contains instead of both antimony andcopper, only one of these metals.

Example 3 A charge composed of 46% tin, 34% lead and 20% antimony ismelted and allowed to cool to 182 C. The mixture of 55 parts'of tin and41.4 parts of lead with the allowable proportion of 3.5 parts of anti-.mony remains fluid and is drawn off, while the main quantity ofantimony is left behind in the solid state.

The process just described can be carried out in reverberatory furnacesdiffering from the ordinary types of such furnaces only in that thedimensions, especially as regards depth of hearth, must be large enoughto allow the molten material to cool so slowly that the crystallizingcomponents separate from those which remain fluid; in other words, thematerial f must not solidify throughout.

The process may be carried out for exam# le in a cylindrical furnacerotatable about its longitudinal axis, as commonly used for meltingcopper.

A furnace of this nature is illustrated in Figure 1 in cross-section.

This furnace comprises a casing 1 'with a lining 2 of refractorymaterial. The end faces of thev furnace have a heat-resisting Wall '3extending vertically alongtwo-thirds of the said faces. A gas burner(not shown) is above the said wall at one end of the'furnace, theproducts of combustion escaping.

at. the other end. The material to be melted is introduced through acharging hole 4, whereafter 'heat is applied until all the charge ismelted. IThe supply of heat is now discontinued and'the furnace isallowed to cool slowly. It cools Von all sides so that a crystallizedouter layer 5 is formed while the centre or core 6 remains. fluid. Apyrom-- eter shows when thc cooling reaches the desired point and a taptube 7 (suitably extended into the interior of the furnace)` is openedso that the said fluid centre o r corel flows out bv gravity since airis allowed to4 pass through the. porous crystalline outer layer.' Thefurnace is mounted. on rollersr8 so that it may be tilted by means of asuitmoving the fluid material.

The furnace shown in cross-section in'Figure 2 has proved particularlysuitable for carrying out the present process. i This furnace,preferably rectangular or circular in cross-section, comprises a hearthmade of fire-resisting material 9 and considerably deeper than in theusual reverberdischarged through a chimney 12.

. able gear for the purpose ofcompletely re-kantimony and co i smallamounts o 'and which may contain smal The charge is allowed to coolafter it has been melted. In this case it-cools from the surface, sothat the crystallized components form an upper layer 13 while those thatremain fluid are at 14 in the lower portion of the hearth. They can thusbe drawn intoa receptacle 16 through a tap hole 15. As shown in thedrawings, the floor of the hole.

What I claim is y 1. A process-for extracting, from lead and tin alloyscontaining antimony and copper and which may contain small amounts ofother metals, an alloy known as tin mixture and being a eutectic mixturecontaining from 54.5 to 55% of tin, not more than 3.6% of antimony, notmore than 0.2% of copper, the remainder bein lead, said processconsisting in meltin immediately heart-l1 hassurfaces inclined towardsthe tap as a whole, without any revious treatment such vas liquation,the sald starting allo slight percentage of antimony and co per remainsfluid, y. and ,drawing of said uid mixture. i

2. A process for extracting, from lead and tin alloys containingantimony and copper' amounts of other metals. an alloy known as tinmixture and being a eutectic mixture containing from 54.5 to 55% of tin,not more than 3.6% of antimony, not more than 0.2% of v copper, theremainder being lead, said process consisting inv selecting saidstarting alloys so that the lead and tin are in the proportions of thesaid eutect-ic mixture, melting said alloys, cooling the molten materialuntil onlyamixture of lead andvtn with only a slight percentage ofantmon and copper remains fluid, Aand drawing o said fluid mixture.

3. The process for extracting tin mix-` ture from lead and, tin allo scontaining per and whic may contain other metals, in which al- 10Ucooling the molten material until only t e said mixture of lead and tinwith only a' loys the proportion of tin is such that practically all thelead is combined with tin to form therewith a eutectic mixture, therebeing enough tin left to form with the other metals including copper andantimony an alloy having the required composition for use as a bearingmetal, which process consists in melt-ing said alloys, coolin the moltenmaterial until only a mixture o lead and tin with a practicallynegligible per- 10 centage of antimony and copper remains fluid, andseparating the fluid tin mixture from the solid portion forming thebearing metal.

In testimony whereof I have aiiixed my 15 signature.

MAX SPEICHERT.

